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Lead-free dielectric ceramic capacitors are extensively studied for their environmental protection and excellent electrical properties. In this study, (1- x) Bi 0.47 Na 0.47 Ba 0.06 TiO 3 - x MgTiO 3 was synthesized by the classical solid-phase method. Perovskite materials usually have a complex structure, and the modification of the A-site and B-site doping can have a wonderful effect on the material. The effect of A-site Mg2+ doping on the phase structure and electrical properties of (1- x)BNBT- x MT was studied. Results showed that a wider optical band gap and a higher grain boundary density can be obtained by doping at the A-site, which greatly improved the breakdown electric field of the ceramics. X-ray diffraction, Raman scattering, transmission electron microscopy, and dielectric constant curves of (1- x)BNBT- x MT ceramics were also performed to characterize the transition between rhombohedral and tetragonal phases. The findings indicated that that doping at the A-site successfully induced the polar nanoregion, and the 0.94Bi 0.47 Na 0.47 Ba 0.06 TiO 3 -0.06MgTiO 3 relaxation ferroelectric ceramics had high W rec (5.82 J/cm3), stable frequency (W rec = 2.53 J/cm3±3 %, 1–200 Hz), excellent temperature stability (W rec ≈2.37 ± 3 % J/cm3, 30–100 °C), and fast discharge rate (4μs). This work can provide ideas for the development of green and harmless dielectric capacitors with high charge/discharge rate and high energy-storage density. [ABSTRACT FROM AUTHOR]

The hardening of (Bi0.5Na0.5)0.85Ba0.15TiO3 (BNBT15) piezoelectric ceramics was investigated by adding raw materials with Bi0.5Na0.5MnO3 (BNM). BNBT15-BNM exhibited a single phase of BNBT15. BNM acts as a sintering aid for BNBT15 to produce domain pinning, and produces tetragonality based on BaTiO3 for increased stability. BNBT15-BNM hardens piezoelectric material with low Mn content, increasing the coercive field and mechanical quality factor. The mechanical quality factor of BNBT15-BNM (0.75 wt%) exceeded 1200. In high-power conditions, BNBT15-BNM (0.75 wt%) exhibited a vibration velocity twice that of hard-PZT. The quality factor gradually decreased with a high vibration velocity. The equivalent stiffness slightly decreased with strain, and the mechanical nonlinearity was much less than that of hard-PZT. BNBT15-BNM (0.75 wt%) has superior high-power properties, and is expected to be a candidate material for use in lead-free piezoelectric ceramics in high-power applications. [ABSTRACT FROM AUTHOR]

Wearable energy harvesters and sensors have recently attracted significant attention with the rapid development of artificial intelligence and the Internet of Things (IoT). Compared to high-output bulk materials, these wearable devices are mainly fabricated by thin-film-based materials that limit their application. Therefore, the enhancement of output voltage and power for these devices has recently become an urgent topic. In this paper, the lead-free bismuth titanate-barium titanate (0.93(Na0.5Bi0.5)TiO3-0.07BaTiO3(BNBT)) nanoparticles and nanofibers were embedded into the PVDF nanofibers. They produced high inorganic electrical voltage coefficients, high electromechanical coupling coefficients, and environmentally friendly properties that enhance the electromechanical performance of pure PVDF nanofibers, and they are all the critical requirements for modern flexible pressure sensors. In detail, PVDF and PVDF-based composites nanofibers were prepared by electrospinning, and different flexible sandwich composite devices were fabricated by the PDMS encapsulation method. As a result, the six-time enhancement maximum output voltage was obtained in a PVDF-BNBT (fiber)-based composite sensor compared to the pure PVDF one. Our results indicate that the output voltage of the pressure sensors has been significantly enhanced, and the development gate is enabled by analyzing the related physical process and influence mechanism.

A ferroelectric material (Bi0.5Na0.5)0.935Ba0.065TiO3 (BNBT) with a perovskite structure was poled and characterized by electrical impedance spectroscopy as a function of temperature, X-ray diffraction, and Rietveld refinement. The ac conductivity showed a low-frequency dispersion, supporting the idea of heterogeneous potential wells favored by Bi3+, Na+, and Ba2+ on the A site of the perovskite type of structure. The activation energies for ac conduction depende on the studied frequency. The permittivity and electrical modulus showed a distribution of the relaxation time associated with the delay in the orientation of the dipoles and an important contribution to the short-range conductivity. [ABSTRACT FROM AUTHOR]

In this study, the photovoltaic ( PV) effect in Fe-doped (Bi0.5Na0.5)TiO3-0.06BaTiO3 ( BNBT) ceramics was investigated. It was found that the bandgap of BNBT is successfully narrowed through Fe doping and a substantially enhanced photovoltaic response was obtained in Fe-doped BNBT. Density functional theory calculations show that the enhanced PV response can be attributed to the dopant, which introduces localized intermediate states within the band gap as well as a strong asymmetry of the projections of the responsible Fe-Ti bond length on the c-axis. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the photovoltaic properties of Nb doped (Bi0.5Na0.5) TiO3–xBaTiO3 (BNBT) ferroelectric ceramics prepared by spark plasma sintering (SPS) were investigated and compared with the conventionally sintered (CS) samples. Much higher photocurrent and photovoltage were observed in SPS samples due to their more compact and homogenous microstructures with smaller grain size. Nb doping increases the photovoltaic response of SPS BNBT ceramics significantly. Optimal photovoltaic response is obtained for 1at.% Nb doped SPS BNBT ceramics with a large above-bandgap photovoltage, showing the potential in future photovoltaic application. [Copyright &y& Elsevier]

Wearable energy harvesters and sensors have recently attracted significant attention with the rapid development of artificial intelligence and the Internet of Things (IoT). Compared to high-output bulk materials, these wearable devices are mainly fabricated by thin-film-based materials that limit their application. Therefore, the enhancement of output voltage and power for these devices has recently become an urgent topic. In this paper, the lead-free bismuth titanate-barium titanate (0.93(Na0.5Bi0.5)TiO3-0.07BaTiO3(BNBT)) nanoparticles and nanofibers were embedded into the PVDF nanofibers. They produced high inorganic electrical voltage coefficients, high electromechanical coupling coefficients, and environmentally friendly properties that enhance the electromechanical performance of pure PVDF nanofibers, and they are all the critical requirements for modern flexible pressure sensors. In detail, PVDF and PVDF-based composites nanofibers were prepared by electrospinning, and different flexible sandwich composite devices were fabricated by the PDMS encapsulation method. As a result, the six-time enhancement maximum output voltage was obtained in a PVDF-BNBT (fiber)-based composite sensor compared to the pure PVDF one. Our results indicate that the output voltage of the pressure sensors has been significantly enhanced, and the development gate is enabled by analyzing the related physical process and influence mechanism. [ABSTRACT FROM AUTHOR]

Abstract: (Bi0.5Na0.5)0.94Ba0.06TiO3 + x wt% Dy2O3 with x =0–0.3 ceramics were synthesized by conventional solid-state processes. The effects of Dy2O3 on the microstructure, the piezoelectric and dielectric properties were investigated. X-ray diffraction pattern confirmed that the coexistence of tetragonal and rhombohedral phases in the (Bi0.5Na0.5)0.94Ba0.06TiO3 composition was not changed by adding 0.05–0.3wt% Dy2O3. SEM images indicate that all the ceramics have pore-free microstructures with high density, and that doping of Dy2O3 inhibits the grain growth of the ceramics. The addition of Dy2O3 shows the double effects on decreasing the piezoelectric and dielectric properties for 0< x <0.15 when Dy3+ ions substitute B-site Ti4+ ions, and increasing the properties for 0.15< x <0.3 when Dy3+ ions enters into A-site of the perovskite structure. The optimum electric properties of piezoelectric constant d 33 =170pC/N and the dielectric constant ɛ r =1900 (at a frequency of 1kHz) are obtained at x =0.3. [Copyright &y& Elsevier]

Abstract: A systematic XRD investigation of poled and unpoled ceramics of the system (1− x) Bi0.5Na0.5TiO3–x BaTiO3 (0≤ x ≤0.2) (BNBT) was performed. The variation of the lattice parameters confirms the existence of a morphotropic phase boundary at 0.06≤ x ≤0.08; however, significant differences in unit cell parameters between poled and unpoled states appear. Lattice distortions of the rhombohedral and tetragonal phases are significantly increased in poled samples. Dramatic changes in peak intensities of the pseudo-cubic (200) reflections between poled and unpoled samples reveal a strong enhancement of the tetragonal volume fraction in the poled state. Temperature-dependent XRD studies confirm a transition into a cubic high-temperature phase. This transition is rather smooth in the unpoled state. In poled samples, the tetragonal distortion and the tetragonal volume fraction display a different temperature variation and tetragonal regions seem to persist into the cubic phase field. [Copyright &y& Elsevier]